from more learned people than me on mx5nutz ;-
It stops the ISCV from fighting against engine braking unless you are in neutral or have the clutch depressed.
Idle speed stabilisation in the ECU depends on several inputs (clutch, neutral, sidelights, air-con, blower motor, idle). There is a Switch Monitor diagnostic mode built into the ECU
The idle circuit is live in gear with no throttle so that the car doesn't stall and allow you to trickle in traffic
now how you stop it doing its thing I don't know
